Known belt drives, such as for driving an internal combustion engine camshaft, are normally used in dry applications, in which a tightener is used to maintain correct tension of the belt.
Cam tighteners for dry applications are known comprising a fixed member with a supporting pin; a spring-loaded cam arm; an idle pulley fitted to the cam arm and cooperating with a timing belt; and a bushing of friction material interposed radially between the fixed pin and the cam arm to damp vibration of the belt.
For applications in the presence of oil, chains are normally used, which cooperate with a shoe to maintain correct tension.
Belt applications in the presence of oil have recently been developed, in which known tighteners have proved ineffective in maintaining correct tension.